Sound generator

ABSTRACT

An improved whistle for sound generation having a unitary stem and body, combined with a simplified plug type mount provides a robust readily installed whistle of predetermined stable resonance characteristic for commercial application.

United States Patent 91 Bruinsma et a1.

[ Oct. 30, 1973 SOUND GENERATOR [75] Inventors: Bote Gosse Bruinsma, Como,

Quebec; Eustace Cosmo Shuffler,

[73] Assignee: Dominion Engineering Works,

Limited, Lachine, Quebec, Canada 22 Filed: July 19,1971

211 Appl.No.:163,784

[30] Foreign Application Priority Data July 29, 1970 Canada 89426 [52] U.S. CI. 116/137 A, 34/D1G. 14, 259/1 [51] Int. Cl 1306b 3/00 [58] Field of Search 116/137, 137 A;

259/1 DIG. 42, DIG. 43, DIG. 44; 239/102, 4, 521, 523; 55/178; 34/D1G. 13, DIG. 14

[56] References Cited UNITED STATES PATENTS 3,070,313 12/1962 Fortman 116/137 A X 3,084,868 4/1963 FaIer et a1 116/137 A X 3,107,647 10/1963 Soloff 116/137 A 3,125,986 3/1964 Fonman et a1. 116/137 A 3,226,029 12/1965 Goodman et al. 116/137 A X 3,302,301 2/1967 Goble 116/137 A X FOREIGN PATENTS OR APPLICATIONS 219,328 3/1969 U.S.S.R 239/102 Primary Examiner-Louis J. Capozi Attorney-Raymond A. Eckersley et al.

[57] ABSTRACT An improved whistle for sound generation having a unitary stem and body, combined with a simplified plug type mount provides a robust readily installed whistle of predetermined stable resonance characteristic for commercial application.

4 Claims, 2 Drawing Figures PAIENIEflnm so ms 3.1683137 INVENTOR. BOTE G. BRUINSMA EUSTACE C. SHUFFLER BY T 47 Patent Agent SOUND GENERATOR This invention is directed to an improved whistle for use in sonic processes.

The use of sound fields for carrying out industrial processes such as the drying of paper or other webs is dependant upon the provision of robust readily mounted whistles for stable operation at predetermined frequencies and intensities.

The present invention provides an improved stem jet whistle of robust construction to provide stable, reliable operation. A further aim of the invention is to provide a whistle adapted for ready mounting in a sound reflector or in the wall of an air or gas supply conduit.

Previous work on stem jet whistles by Hartmann resulted in whistles of generally low efficiency, in the order of to percent efficient. One characteristic individual stem jet whistles of the prior art utilised a slender stem of about one-sixteenth inch diameter supporting an axially adjustable resonator cup, the stem being centered relative to a knife-edged nozzle by means of three adjustable set screws.

Quite apart from the difficulties inherent in producing a whistle of this prior art type to suitable accuracy limits for acceptable repeatability of the sound production characteristic, the low efficiency and susceptibility to damage from air-entrained particles make such prior art whistles quite unattractive for commercial production and utilization.

The subject stem jet whistle is provided with an externally threaded body akin to that of an automotive spark plug, having an integral stem portion extending axially from the whistle body. Thewhistle body serves to both mount the whistle and connect the inlet thereof to a gas supply manifold. A skirt portion secured to the whistle body extends axially therefrom about the stem. A plurality of gas apertures arranged symmetrically about the stem connects the annular space formed between the skirt portion and the stem with the interior of the whistle. A resonator cup attached to the outer end of the stem in facing relation with the skirt and axially displaced therefrom defines an annular sound outlet.

The problem which presents itself in the continuous functioning of stem jet whistles, namely the susceptibility of whistles to damage and malfunction when operatedwith impure air as provided by commercial compressors, stems from the presence of minute particles such as carbon entrained in the air which erode the nozzle or become deposited on the resonator cup thus damaging or changing the resonance characteristic of the whistle. By skewing the internal passages within the whistle controlled swirling of the whistle air may be promoted, tending to centrifuge the air, whereby the path of particles passing through the whistle is modified and the tendency to particle damage is somewhat reduced, thereby reducing the degree of air filtering capacity required in the plant. In addition, the avoidance of a sharp edged nozzle at the whistle outlet, by the provision of an annular end band at the nozzle, renders the whistle less susceptible and sensitive to erosion damage of the nozzle. Further, the annular nozzle band, which faces generally axially of the whistle serves as a reflecting surface to enhance effective sound generation.

Certain embodiments of the present invention are described, reference being had to the accompanying FIG. 1 which shows a partially sectioned view of a stem jet whistle embodying features of the present invention;

and FIG. 2 which is a half plan view of the embodiment of FIG. 1.

Referring to the drawing, the whistle 10 comprises a body portion 1 l, the upper end thereof having threads 12 thereon for mounting purposes, terminating at shoulder 15, which is hexagon headed to accept a standard sized wrench.

A stem 14 extends from the body 11, with three inclined bores 16 shown adjacent thereto communicating with the internal bore 18 of the body 11.

A tube portion 20 of barrelled form is secured at its upper end 21 to the body 11 as by swaging. The use of welding, brazing or adhesives and bonding agents such as epoxy resin for the purpose of securing the tube portion 20, or the use of a shrinkage fit is contemplated.

A resonator cup 25 is secured to the lower end of stem 14 as by swaging, the cup 25 having a sharp edged lip 26 in facing relation with the annular nozzle orifice 23 formed between stem 14 and the skirt portion 22 of the tube 20. The outlet bore or orifice 23 terminates at annular land 24, illustrated as being inclined normally to the whistle main axis, and forming a reflecting surface in co-operation with the cup 25. The radial extent of the annular orifice 23 is indicated by way of an arrowed dimension line in FIG. 2.

While the illustrated resonator cup 25 is of cylindrical form, the adoption of cups having conical section also is contemplated, whereby the effective cup diameter may be favourably increased, for enhanced performance using hot air as the energizing medium.

A sealing gasket G such as a hollow copper gasket of the spark plug type is illustrated.

One formulation which operated economically on low pressure air in the range 27-45 psig was provided with the following parameters:

Stem 0.187 inch dia. Nozzle 0.234 inch dia. Resonator cup 0.376 inch dia.

0.147 inch depth Nozzle to resonator clearance 0.095 inch Variations of the above parameters enable the attainment of a frequency range from 12 to 20 Kilohertz, and enable sound pressure level in the order of decibel to be achieved when used in conjunction with a suitable reflector, and using air of 200 F or higher. Efficiencies in excess of 30 percent may thus be achieved.

The nozzle K factor, the ratio of resonator diameter to nozzle diameter, lies in the range 1.5 to 2.0.

The relatively large stem diameter, in addition to providing a strong cup support, exceeds the stem diameter of previous Hartmann whistles by a ratio of two or three to one. This increase in stem diameter reduces equivalent nozzle outlet area by at least 25 percent, to provide enhanced operating characteristics.

The use of a relatively large diameter stem also enhances flow conditions within the whistle whereby the internal flow path is minimised and the internal pressure drop correspondingly reduced.

The degree of skewing contemplated for the air passages or bores 16, if used, is selected in accordance with a desired compromise between centrifuging effect and pressure recovery characteristic.

While the illustrated embodiment relies upon a threaded mounting arrangement the alternative adoption of a bayonet type fitting having a multi-start thread or cam is also contemplated.

The improved whistle according to the present invention provides the following additional unobvious advantages and functional characteristics:

Simple rugged construction suited to mass production and ready installation; large rugged stem permits increased diameter of nozzle and resonator, while maintaining stable operation over wide range of air pressure; operates with high efficiency at gas temperatures in excess of 200 F.

While the plug type mount is shown by which the whistle is inserted from the sound chamber side of the gas supply manifold, it will be understood that the threaded barrel portion may extend oppositely so as to permit threaded insertion of the whistle into the sound chamber.

The provision of individual air supply by hose attachment also is contemplated.

I claim:

1. A unitary stem jet whistle for use with moderate air pressure in the range 27 to 45 psig and operable at a predetermined fixed frequency in the range 12-20 kilohertz comprising a hollow body portion having a gas inlet, and a gas outlet nozzle spaced therefrom, a substantially stiff stem portion cantilevered from within the body and extending therefrom through the aperture of the nozzle, the nozzle having an outlet bore of limited axial extent, a cup-like resonator secured to the stem externally of the nozzle and in facing relation therewith to define an annular exhaust passage, the value K of the ratio of the nozzle cup diameter to the inner diameter of the nozzle bore lying in the range 1.5 to 2.0.

2. The unitary whistle as claimed in claim 1, said nozzle having an external peripheral annular land inclined to the polar axis of the whistle.

3. The whistle as claimed in claim 2 having thread attachment means on an external surface thereof for attachment of the whistle.

4. The whistle as claimed in claim 1, having said stem portion extending centrally within the body being of fixed length and defining an annular gas flow passage therewith, and a plurality of bores providing gas flow connection between the annular passage and said gas inlet, said bores being skewed at a selected angle to the whistle main axis to provide a desired centrifuging effeet on air passing therethrough. 

1. A unitary stem jet whistle for use with moderate air pressure in the range 27 to 45 psig and operable at a predetermined fixed frequency in the range 12-20 kilohertz comprising a hollow body portion having a gas inlet, and a gas outlet nozzle spaced therefrom, a substantially stiff stem portion cantilevered from within the body and extending therefrom through the aperture of the nozzle, the nozzle having an outlet bore of limited axial extent, a cup-like resonator secured to the stem externally of the nozzle and in facing relation therewith to define an annular exhaust passage, the value K of the ratio of the nozzle cup diameter to the inner diameter of the nozzle bore lying in the range 1.5 to 2.0.
 2. The unitary whistle as claimed in claim 1, said nozzle having an external peripheral annular land inclined to the polar axis of the whistle.
 3. The whistle as claimed in claim 2 having thread attachment means on an external surface thereof for attachment of the whistle.
 4. The whistle as claimed in claim 1, having said stem portion extending centrally within the body being of fixed length and defining an annular gas flow passage therewith, and a plurality of bores providing gas flow connection between the annular passage and said gas inlet, said bores being skewed at a selected angle to the whistle main axis to provide a desired centrifuging effect on air passing therethrough. 